I have not been feeling well and the doctor did a cbc. my white count was 18.8 and platelets were 435. they say it is colitis.could it be leukemia?

F/u with your MD: You've been seen and examined by your doctor who concluded that colitis is the problem with you, correct?. My suggestion is to listen to your doctor and f/u with him/her. Infection or inflammation like colitis certainly can increase your white blood cells and your platelet. While anything is possible in the world- you've got to remember that common things happen commonly. Infection is more common.

Tough : There is such a large differential for elevated wbc. Most often it's due to infection/inflammation. If u have a reason to have elevated WBC such ad colitis, then nothing to worry about. It should come back to normal once the initial process is resolved. It should be repeated again to make sure it is coming down.